In the natural gas industry, it is common to distribute the gas through a rigid, steel pipe having a circular cross-section and called a "carrier" pipe. The carrier pipe is sheathed by a large diameter "casing" such as plastic wrap.
In making repairs, replacements or modifying distribution systems, operating crews frequently have to remove the rigid casing from the carrier pipe. Removal of the casing may be accomplished by cutting the casing about a circumference at spaced intervals so that the casing is in segments, and then removing the individual segments between the peripheral cuts using an axial pipe cutter. A conventional axial pipe cutter or casing splitter, as it is sometimes referred to, has a carriage mounted on a frame, and the carriage is moved manually back and forth along the frame after the frame is mounted to the casing. The manual reciprocation of the cutter is by means of a long lever arm. Not only is it time consuming and tiring to remove pipe casing in this manner, but it is frequently difficult or very inconvenient to do so, particularly when the section of casing to be removed is located in a difficult location. Moreover, it is frequently inconvenient or difficult to locate the manual pipe cutter at a radial location about the circumference of the casing other than on top of the casing because the actuating lever arm must be located in a position to be conveniently forced back and forth by a person and access ditches are formed only as large as needed.
The present invention includes an axial pipe splitter (which may be the conventional manual cutter described above) having a carriage and rotary cutter wheels mounted for reciprocation on a frame. In the present invention, the frame is extended axially of the pipe, and a hydraulic motor is mounted on the frame off one end of the carriage. The drive shaft of the motor is provided with a rotary crank in the form of a disk, and a drive arm is connected between the rotary crank and the carriage of the cutter so that as the motor rotates, the rotary crank and drive arm convert the rotational motion of the motor drive shaft to a reciprocating motion of the carriage.
The frame of the apparatus in the disclosed embodiment is extended to the other side of the carriage (that is, to the side distal from the motor mounting); and this second frame extension is provided with a stabilizer assembly which may be adjusted radially of the pipe to engage directly the carrier pipe and to grip it with a pair of pads to stabilize the frame of the apparatus as the cutter carriage is reciprocated back and forth. This prevents the frame and the cutter carriage from creeping in an axial direction.
In the course of a particular cut, it is necessary for an operator to tighten the carriage so that the rotary cutters are forced further into the casing as the outer portions of the casing are cut. To accomplish this safely, the motor is provided with a speed control device so that the operator may slow the motor down, or stop it, while making this adjustment. Further, in a preferred embodiment, the hydraulic valve which controls the speed has a lever arm, and the apparatus is provided with a locking mechanism to secure the speed control operating arm in the stopped position. This safety feature prevents inadvertent actuation of the cutter carriage, for example, when the device is being moved to a new cutting location.
Other features and advantages of the present invention will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in the various views.